Metallic glass, magnetic recording medium using the same, and method of manufacturing the magnetic recording medium

ABSTRACT

The present invention provides a metallic glass having a chemical composition represented by any one of the following formulae (1) to (3): 
       Fe m Pt n Si x B y P z  (wherein, 20&lt;m≦60 at %, 20&lt;n≦55 at %, 11≦x&lt;19 at %, 0≦y&lt;8 at %, and 0&lt;z&lt;8 at %)  (1);
 
       Fe 55 Pt 25 (Si x B y P z ) 20  (wherein, 11≦x&lt;19 at %, 0≦y&lt;8 at %, and 0&lt;z&lt;8 at %)  (2); and
 
       (Fe 0.55 Pt 0.25 Si 0.16 B 0.02 P 0.02 ) 100 - x M x  (wherein, 0&lt;X≦6 at %; and M represents an element or a combination of any two or more of the elements selected from Zr, Nb, Ta, Hf, Ti, Mo, W, V, Cr, Mn, Al, Y, Ag, and rare earth elements.)  (3).
 
     The present invention provides a magnetic recording medium  1  comprising: a substrate  11 ; and a metallic glassy layer  12  that is arranged on the substrate  11  and has a plurality of convex portions  12 A and concave portions  12 B. The metallic glassy layer  12  has a chemical composition represented by any one of the above formulae (1) to (3).

TECHNICAL FIELD

The present invention relates to a metallic glass, more specifically,the metallic glass having a chemical compositionFe_(m)Pt_(n)(Si_(x)B_(y)P_(z)), a magnetic recording medium using thesame, and a method of manufacturing the magnetic recording medium.

BACKGROUND ART

With the development of advanced information society in recent years,the need for larger capacity image information recording is increasing,and a surface recording density as high as 1 Terabit per square inch(Tb/inch²) is required for magnetic recording media. As a magneticrecording medium providing such high recording density, a patternedmagnetic recording medium, which isolates magnetic dots using anonmagnetic material, has been a focus of attention (See Non-patentReference 1.).

The technique described in Non-patent Reference 1 uses a mask on whichresist is patterned by the nanoimprint technology, and isolates magneticdots by etching a magnetic film using this mask.

It is known that a rapidly quenched Fe—Pt—B alloy ribbon has adouble-phase structure consisting of a uniform nanosized amorphous phaseand a fcc(γ)-FePt phase, and that structure transforms into ananostructure exhibiting good hard magnetic property by heat treatment(See Non-patent Reference 2.).

-   [Non-patent Reference 1] Tsutomu AOYAMA, Isamu SATO, Shunji ISHIO,    “Fabrication and magnetic properties of patterned magnetic recording    media”, OYO BUTURI, 2003, Vol. 72, No. 3, pp. 298-303-   [Non-patent Reference 2] A. Inoue and W. Zhang, J. Appl. Phys., 97,    10H308, 2005

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

With the conventional patterned magnetic recording media as described inNon-patent Reference 1, since the resist is nanoimprinted, dot pitch isas large as 100 nm or larger. It is therefore difficult to achieve asurface recording density as high as 1 Tb/inch². In addition, each ofthe magnetic recording media must undergo a series of fabricationprocesses as described in Non-patent Reference 1, which increases theprocessing cost.

Accordingly, the object of present invention is directed to provide ametallic glass, a magnetic recording medium using the metallic glass,and a method of manufacturing the magnetic recording medium thatsubstantially obviate above mentioned problems due to limitations anddisadvantages of the related arts.

Means to Solving the Problems

To achieve the above objectives, the present invention provides ametallic glass characterized in that its chemical composition isrepresented by formula (1) as shown below.

Fe_(m)Pt_(n)SixB_(y)P_(z) (wherein, 20<m≦60 at %, 20<n≦55 at %, 11≦x<19at %, 0≦y<8 at %, and 0<z<8 at %)  (1)

The metallic glass represented by the above formula preferably has achemical composition represented by formula (2) as shown below.

Fe₅₅Pt₂₅(Si_(x)B_(y)P_(z))₂₀ (wherein, 11≦x<19 at %, 0≦y<8 at %, and0<z<8 at %)  (2)

An another metallic glass of the present invention is characterized inthat its chemical composition is represented by formula (3) as shownbelow.

(Fe_(0.55)Pt_(0.25)Si_(0.16)B_(0.02)P_(0.02))_(100-x)M_(x) (wherein,0<x≦6 at %; and M represents an element or a combination of any two ormore of the elements selected from Zr, Nb, Ta, Hf, Ti, Mo, W, V, Cr, Mn,Al, Y, Ag, and rare earth elements.)  (3)

In the chemical composition of the metallic glass represented by formula(3), M may be substituted by Zr. In the chemical composition of themetallic glass represented by formulae (1) to (3), a part of Fe may besubstituted by Co or Ni, and a part of Pt can be substituted by Pd.

In another aspects, the present invention provides a magnetic recordingmedium characterized in that it comprising: a substrate; and a metallicglass layer, which is formed on the substrate and has a plurality ofconcave portions and convex portions, and the metallic glass layer ismade of a metallic glass having a chemical composition represented byformula (1) as shown below, wherein concave portions are consisting of asoft magnetic layer, and convex portions are consisting of a hardmagnetic layer.

Fe_(m)Pt_(n)Si_(x)B_(y)P_(z) (wherein, 20<m≦60 at %, 20<n≦55 at %,11≦x<19 at %, 0≦y<8 at %, and 0<z<8 at %)  (1)

Preferably, the chemical composition is represented by formula (2) asshown below.

Fe₅₅Pt₂₅(Si_(x)B_(y)P_(z))₂₀ (wherein, 11≦x<19 at %, 0≦y<8 at %, and0<z<8 at %)  (2)

Furthermore, the metallic glass may have a chemical compositionrepresented by formula (3) as shown below.

(Fe_(0.55)Pt_(0.25)Si_(0.16)B_(0.02)P_(0.02))₁₀₀-_(x)M_(x) (wherein,0<x≦6 at %; and M represents an element or a combination of any two ofmore of the elements selected from Zr, Nb, Ta, Hf, Ti, Mo, W, V, Cr, Mn,Al, Y, Ag, and rare earth elements.)  (3)

In the above chemical composition, the concave portions and convexportions preferably has a surface protective layer covered with anonmagnetic material, and the surface of the surface protective layer isflat. The concave portions and convex portions are preferably aligned ina matrix, houndstooth-check, or line sequence pattern.

In the chemical composition of the metallic glass represented by formula(3) as shown above, M may be substituted by Zr. In the chemicalcomposition of the metallic glass represented by formulae (1) to (3)shown above, a part of Fe may be substituted by Co or Ni, and a part ofPt may be substituted by Pd.

In another aspects, the present invention provides a method ofmanufacturing a magnetic recording medium characterized in that itcomprises steps: of forming a metallic glass layer on a substrate;forming concave portions and convex portions on the metallic glass layerusing a mold; and processing a heat treatment of the convex portions ofthe metallic glass layer to have a hard magnetic property, wherein themetallic glass layer has a chemical composition represented by formula(1) as shown below.

Fe_(m)Pt_(n)Si_(x)B_(y)P_(z) (wherein, 20<m≦60 at %, 20<n≦55 at %,11≦x<19 at %, 0≦y<8 at %, and 0<z<8 at %)  (1)

The metallic glass preferably has a chemical composition represented byformula (2) as shown below.

Fe₅₅Pt₂₅(Si_(x)B_(y)P_(z))₂₀ (wherein, 11≦x<19 at %, 0≦y<8 at %, and0<z<8 at %)  (2)

More preferably, the metallic glass may have a chemical compositionrepresented by formula (3) as shown below.

(Fe_(0.55)Pt_(0.25)Si_(0.16)B_(0.02)P_(0.02))_(100-x)M_(x) (wherein,0<x≦6 at %; and M represents an element or a combination of any two ofmore of the elements selected from Zr, Nb, Ta, Hf, Ti, Mo, W, V, Cr, Mn,Al, Y, Ag, and rare earth elements.)  (3)

In the chemical composition of the metallic glass represented by formula(3) as shown above, M may be substituted by Zr. The temperature of theheat treatment of the convex portions on the metallic glass layerpreferably falls within the 750° C. to 850° C. range, and heat treatmentmay be processed for 10 to 30 minutes.

Effects of the Invention

According to the present inventions of the metallic glass, the magneticrecording medium using the same, and the method of manufacturing themagnetic recording medium, finer concave portions and convex portionscan be formed on a ferromagnetic layer made of the metallic glass.Furthermore, since the ferromagnetic material at the convex portionsonly can be made to form a hard magnetic layer, the packing density ofthe magnetic recording medium can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings,

FIG. 1 illustrates the embodiment of magnetic recording medium 1 inaccordance with an embodiment of the present invention, in which (A) isa plain view, and (B) is a cross-sectional view taken along the line A-Ain (A);

FIG. 2 is a cross-sectional view illustrating a typical variation of themagnetic recording medium of the present invention;

FIG. 3 illustrates an another sequence pattern of the convex portions,in which (A) shows a houndstooth-check pattern, and (B) shows a linepattern;

FIG. 4 sequentially illustrates a method of manufacturing a magneticrecording medium according to the present invention;

FIG. 5 illustrates a method of manufacturing a mold;

FIG. 6 sequentially illustrates the method of manufacturing the mold;

FIG. 7 is a chart illustrating the DSC trace of Example 2;

FIG. 8 is a chart illustrating the XRD profiles of Example 2;

FIG. 9 is a chart illustrating the magnetization property of themetallic glass in Example 2;

FIG. 10 is a chart illustrating the dependence of the coercive force ofthe metallic glass in Example 2 on the annealing temperature;

FIG. 11 is a chart illustrating the DSC trace of Example 3;

FIG. 12 is a chart illustrating the XRD profile of Example 3;

FIG. 13 is a chart illustrating the magnetization property of themetallic glass in Example 3;

FIG. 14 is a chart collectively illustrating the XRD profiles of themetallic glasses in Examples 1 to 3;

FIG. 15 is a chart collectively illustrating the magnetizationproperties of the metallic glasses in Examples 1 to 3;

FIG. 16 is a chart illustrating the dependence of parameters on Si and Bcompositions obtained from the magnetization properties of the metallicglasses Fe₅₅Pt₂₅Si_(x)B_(y)P₂, in which (A) shows residual magnetic fluxdensity, (B) shows coercive force, and (C) shows the maximum energyproduct ((BH)_(max));

FIG. 17 illustrates the dependence of the coercive force of the metallicglass Fe₅₅Pt₂₅(Si_(x)B_(y)P_(z)) on the composition of Si, B, and P inExamples 1 to 13; and

FIG. 18 is a chart illustrating the DSC trace of Example 14.

DESCRIPTION OF REFERENCE NUMERALS

-   1: Magnetic recording medium-   11: Substrate-   12: metallic glass layer-   12A: Convex portion-   12B: Concave portion-   13: Surface protective layer-   15: Mold-   15A: Convex portion-   15B: Concave portion-   20: Substrate-   21: SiO₂ film-   22: Mask pattern-   25: Convex portion

BEST MODES FOR CARRYING OUT THE INVENTION

Hereinafter, various embodiments of the present invention will bedescribed in detail with reference to the figures. The same charactersare used to designate same or corresponding components in each figure.

First, favorable forms of the metallic glass of the present inventionare described.

A metallic glass of the present invention is a permanent magnet materialhaving a chemical composition represented by formula (1) as below.

Fe_(m)Pt_(n)Si_(x)B_(y)P_(z) (wherein, 20<m≦60 at %, 20<n≦55 at %,11≦x<19 at %, 0≦y<8 at %, and 0<z<8 at %)  (1)

The chemical composition of the metallic glass of the present inventionis preferably represented by formula (2) shown below.

Fe₅₅Pt₂₅(Si_(x)B_(y)P_(z))₂₀ (wherein, 11≦x<19 at %, 0≦y<8 at %, and0<z<8 at %)  (2)

The metallic glass of the present invention may have a chemicalcomposition represented by formulae (3) shown below.

(Fe_(0.55)Pt_(0.25)Si_(0.16)B_(0.02)P_(0.02))_(100-x)M_(x) (wherein,0<x≦6 at %; and M represents an element or a combination of any two ofmore of the elements selected from Zr, Nb, Ta, Hf, Ti, Mo, W, V, Cr, Mn,Al, Y, Ag, and rare earth elements.)  (3)

Addition of M in the above composition further enhances the metallicglass-forming ability. A preferable material as M is Zr, for example. Inthis case, it is possible to enhance metallic glass-forming ability evenif the composition X of M_(X) exceeds 6 at %. However, since themagnetic property of the metallic glass(Fe_(0.55)Pt_(0.25)Si_(0.16)B_(0.02)P_(0.02))_(100-x) decreases, whichis not desirable, it is preferable to use the metallic glass(Fe_(0.55)Pt_(0.25)Si_(0.16)B_(0.02)P_(0.02))₉₆Zr₄ to obtain sufficientmagnetic property.

A part of Fe of the metallic glassy alloys represented by formulae (1)to (3) shown above can be substituted by Co or Ni, both of which areferromagnetic elements similar to Fe.

A part of Pt of the metallic glassy alloys represented by formulae (1)to (3) shown above can be substituted by Pd for forming L1₀-FePd phase,which will be described later.

The metallic glass of the present invention represented by formulae (1)to (3) as shown above has ferromagnetic property. This metallic glassexhibit soft magnetic property immediately after the formation, butafter annealing at high-temperature for a predetermined period of time,the metallic glass of the present invention exhibits hard magneticproperty due to crystallization.

The metallic glasses of the present invention can be produced frommaster alloys, obtained by melting in a radio-frequency melting furnaceand an arc melting furnace, by the single-roll melt spinning method.

The metallic glass of the present invention is an alloy obtained byadding Si to Fe—Pt—B-P alloy, which has been found to have good magneticproperties by previous research. By adding Si to the above alloyaccording to the present invention, amorphous-forming ability can befurther enhanced. When a melt-spun ribbon is subjected to heattreatment, a composite structure consisting of L1₀-FePt phase, Fe₂Bphase, PtSi phase, and FeSi phase is formed, and the annealed melt-spunribbon exhibits hard magnetic properties because of the L1₀-FePt phase.The alloy that exhibits most favorable amorphous-forming ability hasresidual magnetic flux density (Br) of approximately 0.69 T, coerciveforce (Hc) of 172 kA/m, and maximum energy product of 44 kJ/m³.

It is preferable that the metallic glass of the present invention isproduced by the quenching method having high cooling rate. By cooling amolten material at high cooling rate, finer magnetic particles and anon-equilibrium phase can be formed in the metallic glassy matrix.Specifically, by rapidly quenching the molten material, non-equilibriumphases such as supersaturated solid solution, namely the state in whichadded elements such as B and Si are forcibly dissolved into the metallicglass, and amorphous phase, can be formed easily. These non-equilibriumphases can be transformed into a more stable L1₀-FePt phase easily, andas a result, high coercive force can be obtained.

As a rapid quenching method, it is preferable to use the liquidquenching method, such as single-roll method, double-roll method, andcentrifugal quenching method, and the gas-phase quenching method, suchas sputtering method and vacuum deposition method. By the liquidquenching method, which is known to be useful for manufacturing anamorphous alloy, for example, cooling is performed at the cooling rateas high as 100 K/sec. Consequently, this method is also effective fornon-amorphous alloys to obtain finer crystal grain size and anon-equilibrium phase by the effect of rapid quenching. By the gas-phasecooling method, whose cooling rate is as high as or higher than that ofthe liquid cooling method, allows finer crystal grain size and anon-equilibrium phase to be obtained.

When the metallic glass of the present invention is manufactured by theliquid quenching, melt-spinning method, continuous or discontinuousglassy ribbons in thickness of several μm to several dozen μm can beobtained. The ribbons obtained in this way can also be crushed intopowder. The thin metallic glassy ribbons are ideal as a permanent magnetmaterial for small magnetic parts, with which processing of bulkmaterials incurs high cost and results in degradation of magneticproperty, for example.

The metallic glassy powder obtained by the present invention is ideal asa bonded magnet material, mixed with resin, etc., for example.

According to the present invention, a metallic glassy thin film havingthickness of several nm to several dozen nm can be formed on a substrateby the gas-phase quenching method. The thin film thus formed on asubstrate is ideal as a medium for high-density magnetic recording.Thus, the hard magnetic property can be obtained by without requiringheat treatment or by crystallization by heat treatment at nearly 800 K.Consequently, inexpensive oxide-glass substrates can be used. With themetallic glass of the present invention, since the growth of crystalgrains is suppressed, a very fine crystalline structure can be obtained,which allows the metallic glass of the present invention to satisfy therequirements of high-density magnetic recording media.

It is preferable that heat treatment for crystallization is processed atthe temperature around 800 K, specifically from approximately 750 K to850 K. heat treatment processed at a temperature lower than 750 K is notpreferable because crystallization does not advance and good hardmagnetic property cannot be obtained. In the heat treatment processed at750 K or higher, with the increase of the annealing temperature,crystallization advances and coercive force increases, thus providinghard magnetic property. In the heat treatment processed at 850 K orhigher, since the coercive force is saturated, further temperatureincrease is not necessary.

It is desirable that heat treatment is processed for the time ofapproximately 10 to 30 minutes under the above annealing conditions.Heat treatment processed for less than 10 minutes is not preferablebecause crystallization does not advance and consequently hard magneticproperty cannot be obtained. On the other hand, the heat treatmentprocessed for longer than 30 minutes, the coercive force due tocrystallization is saturated, and so the duration of heat treatment neednot be increased further.

FIG. 1 illustrates an embodiment of magnetic recording medium 1 of thepresent invention, in which (A) is a plain view, and (B) is across-sectional view taken along the line A-A in (A). Magnetic recordingmedium 1 of the present invention comprises: a substrate 11; and ametallic glassy layer 12, which is provided on the substrate 11 and hasa plurality of concave portion and convex portion. The plurality ofconcave portion 12B are a soft magnetic layer. At least outer mostsurface of the plurality of convex portion 12A are consisting of a hardmagnetic layer that allows magnetic recording to be made. For themetallic glassy layer 12, a metallic glass having a chemical compositionrepresented by the above formulae (1) and (2) can be used.

A pitch P of the convex portions 12A is identical to that of a pitch Pof concave portions 12B as shown in FIG. 1, and is set to beapproximately 25 nm. The height t₃ of the convex portions 12A is set tobe approximately 25 nm.

By the way, oxide glasses are used for substrates for conventionalmagnetic recording media, namely a hard disk for Hard Disk Drive.According to the present invention, a metallic glass may be used as thesubstrate 11. When a metallic glass is used as the substrate 11, bulkmetallic glassy material is sandwiched between tools, and by pressingthe bulk material while maintaining it within the supercooled liquidtemperature region, a substrate 11 having a desired thickness can beformed.

At this time, the surface of a mold is mirror-finished by using achemical mechanical polishing (CMP) equipment. The load of the presswork can be minimized by performing press work within the supercooledliquid temperature region of the metallic glass. The mirror-finishedsurface of the mold is copied to the surface of the substrate 11 withmirror accuracy, allowing the substrate 11 to have uniform thicknesshaving excellent evenness or smoothness. Consequently, a metallic glassysubstrate that has undergone press working only can be used as thesubstrate 11, which reduces the machining cost of the substrate 11. Themetallic glassy substrate 11 thus formed can be used not only as amagnetic recording medium but also as a light weight substrate for DVDs,CDs, and HDs.

The metallic glass, which is an amorphous alloy, is high in strength,flexible, and has excellent anti-corrosion characteristics.Consequently, the substrate 11 can be made thin, allowing reduction insize and weight of the magnetic recording medium 1. The magneticrecording medium in the embodiment of the present invention can be usednot only for information recording but also as a scale for magneticrecording media on the order of nanometer (nm).

FIG. 2 is a cross-sectional view illustrating a modified embodiment ofthe magnetic recording medium of the present invention. The magneticrecording medium as shown in FIG. 2 differs from that as shown in FIG. 1that a surface protective layer 13 made of a nonmagnetic material isprovided on convex portions 12A and concave portions 12B. The surfaceprotective layer 13 can cover the concave portions 12B only, or theconcave portions 12B can be filled in and covered along with the surfaceof the convex portions 12A. The surface protective layer 13 can remainflat. As a material for the surface protective layer 13, a SiO₂ film,etc. can be used.

FIG. 3 illustrates an another sequence pattern of convex portions 12A asshown in FIG. 1. FIG. 3(A) shows a houndstooth-check pattern, and FIG.3(B) shows a line shaped pattern. The pitch P of the sequence pattern asshown in FIG. 3(A) is the same as the pattern as shown in FIG. 1,however the pitch between lines P1 is set to be larger than the pitch P.The convex portions 12B can also be arranged in a houndstooth-checkpattern or line shaped pattern as in the case of convex portions 12A.

The concave portions 12B and the convex portions 12A can also be madeinto any patterns at need or arbitrary other than the matrix,houndstooth-check, and line patterns described above. According to thepresent embodiment, since nanoimprint technology is employed to form theconcave portions 12B and convex portions 12A on the metallic glassylayer 12 in an supercooled liquid temperature region as described later,high-precision formation of nano-ordered concave and convex portions canbe possible. High-density magnetic recording media can thus be formedhighly accurately. In addition, since concave portions 12B and convexportions 12A can be formed just by performing press work, processingtime and cost can be minimized.

In the magnetic recording medium 1 as shown in FIG. 1, the convexportions 12B consisting of a soft magnetic layer exist surrounding theconvex portions 12A, which surface consisting of a hard magnetic layer.The concave portions 12B formed by a soft magnetic layer have thefunction to support the recording magnetic field from a magnetic head.Since the recording magnetic field of the magnetic head forms a closingloop while going through the convex portions 12B, fetching of therecording magnetic field and the sensitivity of reading signal can beimproved.

Furthermore, since the convex portions 12B have a surface protectivelayer 13 covered with a nonmagnetic material, each of the hard magneticlayer of the convex portions 12A serves as a magnetically independentrecording bit.

A nonmagnetic material such as aluminum, oxide glass, and metallic glasscan be used as the substrate 11. As described later, the temperature ofthe entire substrate 11 is increased to the molding temperature Tmduring the manufacturing process. When the substrate 11 is an amorphousmaterial, amorphous material in which crystallization temperature ishigher than the molding temperature Tm should be adopted.

The thickness t₁ of the entire metallic glassy layer 12 is approximately20 nm, and the thickness t₂ of the concave portions 12B is approximatelyseveral nm. The area other than the hard magnetic layer of the metallicglassy layer 12 is a soft magnetic layer. This soft magnetic layercorresponds to an interlayer of a conventional perpendicular magneticrecording medium. The recording density as high as 1 Tb/inch² can beachieved by keeping the pitch P of the concave portions 12B formed inmatrix sequence to be approximately 25 nm. The pitch P of the concaveportions 12B is determined by the accuracy of the mold used fornanoimprint molding described previously. When the mold is formed byusing ion beam, etc, the pitch P can be reduced to the order of 10 nm.In this case, the recording density of the magnetic recording medium 1will be increased up to several Tb/inch².

Now, the method of manufacturing the magnetic recording medium 1according to the present invention will be explained below.

FIG. 4 illustrates the method of manufacturing a magnetic recordingmedium according to the present invention. In this embodiment, fineconcave and convex pattern of the metallic glassy layer 12 is formed bythe nanoimprint method. At first, as shown in FIG. 4(A), a metallicglassy layer 12 having a predetermined thickness is formed on asubstrate 11 by the evaporation using sputtering method etc.

Then, as shown in FIG. 4(B), concave portions and convex portions areformed on the metallic glassy layer 12 by the nanoimprint method using amold 15. The mold 15 has convex portions 15A for forming concaveportions 12B on the metallic glassy layer 12 and concave portions 15Bfor forming convex portions 12A on the metallic glassy layer 12. Themethod of manufacturing the mold 15 will be described later.

Amorphous alloys called as metallic glasses feature that the glasstransition temperature Tg is lower than their crystallizationtemperature Tx, and there exists a stable supercooled liquid temperatureregion ΔTx (=Tx−Tg). Within this supercooled liquid temperature region,since the metallic glass exhibits complete Newtonian viscosity flow,low-stress viscosity flow processing can be performed. This is thereason why the metallic glass has excellent micro-formability i.e.micro-configuration transfer property. According to the presentembodiment, using this property of the metallic glass, micro concaveportions and convex portions on the order of nm formed on the mold 15are transferred to a metallic glassy layer 12, thus achieving highlyaccurate and easy micro-/nano-concave and convex formation.

In the process as shown in FIG. 4(B), the substrate 11, on which themetallic glassy layer 12 has been formed, and the mold 15 are heated upto the molding temperature Tm, which is higher than the glass transitiontemperature Tg of the metallic glassy layer 12, and a predetermined loadis applied for a predetermined time, to form a metallic glassy layer 12by imprint molding. The substrate 11 and the mold 15 are then cooled.When their temperature decreases to lower than the glass transitiontemperature Tg of the metallic glassy layer 12, the load is removed.Through these processes, the concave portions 12B having the depth oft₁−t₂ are formed on the metallic glassy layer 12 as shown in FIG. 4(C).

Then, as shown in FIG. 4(D), by annealing the amorphous layer of themetallic glass, the only surface of the convex portions 12A iscrystallized to form a hard magnetic layer. Laser can be used for theheat treatment of the surface of the convex portions 12A.

Amorphous alloys, namely metallic glassy alloys represented by the abovechemical composition formulas (1) to (3) can be used. For example, anamorphous alloy having the composition Fe₅₅Pt₂₅Si₁₆B₂P₂ can preferablybe used. This alloy remains a soft magnetic layer in an amorphous state.When this alloy is processed by heat treatment, it is crystallized andturns into a hard magnetic layer consisting of Fe—Pt phase having L1₀structure. Meanwhile, when a part of Pt is substituted by Pd, a hardmagnetic layer made of Fe—Pd phase having L1₀ structure can be obtainedthrough crystallization processed by the heat treatment.

FIGS. 5 and 6 illustrate how to produce a mold 2. In the first processas shown in FIG. 5(A), a SiO₂ film 21 having a thickness ofapproximately 100 nm is formed on a surface of a Si substrate 20 havinga (100) surface by the thermal oxidation method.

In the second process as shown in FIG. 5(B), a tungsten (W) thin film isformed on the SiO₂ film 21 by the focused ion beam chemical vapordeposition (FIB-CVD) method, and a mask pattern 22 is formed on the SiO₂film 21. The patterning of this tungsten (W) thin film is processed byirradiating Ga⁺ ion beam to the area to be processed while sprayinggasified W(CO)₆ (tungsten hexacarbonyl). A deposited tungsten (W) filmis formed on the surface of the SiO₂ film 21 by decomposition of theW(CO)₆ gas into W and CO. FIG. 5(C) illustrates a mask pattern made of aplurality of masks 22 formed on the SiO₂ film 21.

In the third process as shown in FIG. 6(A), using the tungsten maskpattern 22, the SiO₂ film 21 is etched anisotropically by reactive ionetching (RIE) with CHF₃. As shown in FIG. 6(B), a plurality of convexportions 25 that correspond to the concave portions 12B of the metallicglassy layer 12 are formed on the surface of the mold 15.

In the embodiment described above, the mold 15 which is formed byprocessing the Si substrate 20 by FIB was used, however a mold 15 madeof metallic glass can also be used. In this case, a mother die is formedby processing the Si substrate 20 by FIB, and a mold 15 can be formed byimprinting the metallic glass using the mother die. The surfaceconfiguration i.e. concave portions and convex portions of the motherdie should be identical to that of the metallic glassy layer 12 as shownin FIG. 1.

Example 1

The metallic glass of the present invention will be described further indetail by referring to various Examples below, but the Examples of thepresent invention are not limited to those described.

Using a mother alloy produced by melting in a radio-frequency meltingfurnace and an arc melting furnace, metallic glassy ribbons having thecomposition Fe₅₅Pt₂₅Si₁₃B₅P₂ was produced by the single-roll meltspinning method. The thermal property of a sample having a shape ofribbon of Example 1 was measured by the differential scanningcalorimetry (DSC) to find the supercooled liquid region.

The “supercooled liquid region” determines the resistance tocrystallization, namely the stability and processability, of amorphousmaterial. In the present specification, the supercooled liquid region isdefined as the difference between the glass transition temperature Tgand the crystallization temperature Tx, which can be obtained byconducting differential scanning calorimetry (DSC) at the heating rateof 40 K/min. The difference ΔTx (=Tx−Tg) between the crystallizationstart temperature Tx and the glass transition temperature Tg of themetallic glass in Example 1 was 25 K. The metallic glass in Example 1exhibited enhanced amorphous-forming ability compared with FePtBPmetallic glassy system to which Si was not added.

The sample of Example 1 was encapsulated into a quartz tube in vacuum,and was processed by the annealing for 900 seconds. Phase identificationwas performed by using X-ray diffraction (XRD), and magnetic propertywas measured by using a vibrating sample magnetometer (VSM).

By the heat treatment of the quenched ribbons of Example 1 at thetemperature of 810 K or higher, a composite structure consisting ofL1₀-FePt phase, Fe₂B phase, PtSi phase, and FeSi phase was formed. Inthe metallic glass having the most excellent amorphous-forming ability,the residual magnetic flux density (Br), coercive force (Hc), and themaximum energy product ((BH)max) were approximately 0.69 T, 172 kA/m and44 kJ/m³, respectively.

Example 2

The metallic glass in Example 2 was manufactured by the same method asExample 1, except that the chemical composition was changed toFe₅₅Pt₂₅Si₁₆B₂P₂. ΔTx (=Tx−Tg) was found to be 37 K.

FIG. 7 is a chart illustrating the DSC trace of Example 2. The ordinateaxis represents heat quantity and the abscissa axis representstemperature (K). In general, to examine phase transition phenomenon witha DSC trace, the exothermic reaction is observed. Meanwhile, in themetallic glass, taking into consideration the supercooled liquid regionwhere the endothermic reaction is shown, the downward arrow on theordinate axis is made to represent endotherm. As shown in FIG. 7, ΔTx(=Tx−Tg) of the metallic glass in Example 2 was 37 K.

FIG. 8 illustrates the XRD profiles of Example 2. The ordinate axisrepresents the intensity of X-ray diffraction, and the abscissa axisrepresents the angle (°), which is equivalent to the value twice theangle of incidence (θ) of X-ray into the atomic plane. FIG. 8 indicatesthat the metallic glass having the composition in Example 2 startedprecipitating crystalline phases with the increase of annealingtemperature immediately after the formation of the metallic glass(as-Q), and that L1₀-FePt phase having a hard magnetic property wasformed obviously at 810 K. It is understood that fcc-FePt phase, FeSiphase, and Pt₂Si₃ phase are formed in addition to the L1₀-FePt phase.

FIG. 9 is illustrates the magnetization property of the metallic glassin Example 2. The ordinate axis represents magnetization J (T: Tesla),and the abscissa axis represents magnetic field Hc (A/m). As shown inFIG. 9, the metallic glass having the composition of Example 2 exhibitedsoft magnetic property through the heat treatment processed at 675 K and750 K after the formation of the metallic glass (as-Q), and after theheat treatment processed at 810 K, hard magnetic property was obtained.It is also apparent that in case of B is 2%, the formation of Pt—Siphase is not isolated from the transformation of the Fe—Pt phase.

FIG. 10 illustrates the dependence of the coercive force of the metallicglass in Example 2 on the annealing temperature. The ordinate axisrepresents the coercive force Hc (kA/m), and the abscissa axisrepresents annealing temperature (K). The annealing time is 900 seconds.As shown in FIG. 10, the metallic glass having the composition ofExample 2 exhibited hard magnetic property by the heat treatmentprocessed at 750 K or higher after the formation of the metallic glass.It was also found that the coercive force ranging from 100 kA/m to 170kA/m was obtained at the annealing temperature of approximately 780 K to830 K.

Example 3

The metallic glass in Example 3 was manufactured by the same method asExample 1, except that the chemical composition was changed toFe₅₅Pt₂₅Si₁₈P₂. FIG. 11 illustrates the DSC trace of Example 3. ΔTx wasfound to be 37 K.

FIG. 12 illustrates the XRD profile of Example 3. The ordinate axisrepresents the intensity of X-ray diffraction, and the abscissa axisrepresents angle (°), which is equivalent to the value twice the angleof incidence θ of the X-ray into the atomic plane. FIG. 12 indicatesthat the metallic glass having the composition of Example 3 startedprecipitating crystalline phases with the increase of annealingtemperature immediately after the formation of the metallic glass(as-Q), and that L1₀-FePt phase having a hard magnetic property wasformed obviously at the temperature of 795 K. It is also obvious thatfcc-FePt phase, FeSi phase, and Pt₂Si₃ phase were formed in addition tothe L1₀-FePt phase.

FIG. 13 illustrates the magnetization property of the metallic glass ofExample 3. The ordinate axis represents magnetization J (T: Tesla) andthe abscissa axis represents magnetic field H (A/m). FIG. 13 indicatesthat the metallic glass having the composition of Example 3 exhibitedsoft magnetic property by the heat treatment processed at 750 Kimmediately after the formation of the metallic glass (as-Q), and thathard magnetic property was obtained after by the heat treatmentprocessed at 795 K.

FIG. 14 collectively illustrates the XRD profiles of the metallicglasses in Examples 1 to 3. It is apparent that L1₀-FePt crystallinephase was formed by the heat treatment processed at approximately 795and 810 K.

FIG. 15 collectively illustrates the magnetization properties of themetallic glasses in Examples 1 to 3. It is obvious that the metallicglasses exhibited hard magnetic properties by the heat treatmentsprocessed at approximately 795 and 810 K.

Example 4

The metallic glass in Example 4 was manufactured by the same method asExample 1, except that the chemical composition was changed toFe₅₅Pt₂₅Si₁₅B₃P₂. ΔTx was found to be 37 K.

FIGS. 16 (A) to 16(C) illustrate the dependence of residual magneticflux density, coercive force, and the maximum energy product ((BH)max)on Si and B compositions obtained from the magnetization properties ofthe metallic glasses Fe₅₅Pt₂₅Si_(x)B_(y)P₂ in Examples 1 to 4. The upperabscissa axis represents B composition (at %) and the lower abscissaaxis represents Si composition (at %). As shown in FIG. 16(A), residualmagnetic flux density value of approximately 0.73 T to 0.8 T wasobtained when Si composition varied from 18 at % to 10 at %.

As shown in FIG. 16(B), the coercive force of approximately 164 kA/m to205 kA/m was obtained when Si composition varied from 18 at % to 10 at%.

As shown in FIG. 16(C), the maximum energy product of approximately 49kJ/m³ to 60 kJ/m³ was obtained when Si composition varied from 18 at %to 10 at %.

Consequently, by varying Si and B compositions, the magnetic property ofthe metallic glass having the above composition; Fe₅₅Pt₂₅Si_(x)B_(y)P₂can be changed.

Example 5

The metallic glass in Example 5 was manufactured by the same method asExample 1, except that the chemical composition was changed toFe₅₅Pt₂₅Si₁₁B₁P₈. ΔTx was found to be 26 K.

Example 6

The metallic glass in Example 6 was manufactured by the same method asExample 1, except that the chemical composition was changed toFe₅₅Pt₂₅Si₁₃B₁P₆. ΔTx was found to be 32 K.

Example 7

The metallic glass in Example 7 was manufactured by the same method asExample 1, except that the chemical composition was changed toFe₅₅Pt₂₅Si₁₃B₃P₄. ΔTx was found to be 26 K.

Example 8

The metallic glass in Example 8 was manufactured by the same method asExample 1, except that the chemical composition was changed toFe₅₅Pt₂₅Si₁₄B₄P₂. ΔTx was found to be 27 K.

Example 9

The metallic glass in Example 9 was manufactured by the same method asExample 1, except that the chemical composition was changed toFe₅₅Pt₂₅Si₁₅B₁P₄. ΔTx was found to be 31 K.

Example 10

The metallic glass in Example 10 was manufactured by the same method asExample 1, except that the chemical composition was changed toFe₅₅Pt₂₅Si₁₅B₂P₃. ΔTx was found to be 32 K.

Example 11

The metallic glass in Example 11 was manufactured by the same method asExample 1, except that the chemical composition was changed toFe₅₅Pt₂₅Si₁₅P₅. ΔTx was found to be 17 K.

Example 12

The metallic glass in Example 12 was manufactured by the same method asExample 1, except that the chemical composition was changed toFe₅₅Pt₂₅Si₁₆B₃P₁. ΔTx was found to be 23 K.

Example 13

The metallic glass in Example 13 was manufactured by the same method asExample 1, except that the chemical composition was changed toFe₅₅Pt₂₅Si₁₇B₃. ΔTx was found to be 29 K.

It was found that in any Examples from 4 to 13, L1₀-FePt crystallinephases were produced by the heat treatment, and the hard magneticproperties were obtained.

FIG. 17 illustrates the dependence of the coercive force of the metallicglasses Fe₅₅Pt₂₅(Si_(x)B_(y)P_(z)) on the compositions of Si, B, and Pin Examples 1 to 13. The positions marked with open circles (◯) exhibitthe measured composition of the metallic glass, and the numeric valuesshown next to them represent the coercive force (kA/m). Each of thecurves marked as 160 to 200 displays distributions of the coerciveforce.

It is obvious as shown in FIG. 17 that the high coercive force wasobtained at composition z of P ranging from 2 to 4 at %.

Example 14

The metallic glass in Example 14 was manufactured by the same method asExample 1, except that the chemical composition was changed to(Fe_(0.55)Pt_(0.25)Si_(0.16)B_(0.02)P_(0.02))₉₆Zr₄.

FIG. 18 illustrates the DSC trace of Example 14. The ordinate axisrepresents heat quantity and the abscissa axis represents temperature(K). In general, to examine phase transition phenomenon with a DSCtrace, exothermic reaction is observed. Meanwhile, in the metallicglass, taking into consideration the supercooled liquid region where theendothermic reaction is shown, the downward arrow on the ordinate axisis made to represent endotherm. As shown in FIG. 18, ΔTx (=Tx−Tg) of themetallic glass in Example 14 was 48 K.

From the above, (Fe_(0.55)Pt_(0.25)Si_(0.16)B_(0.02)P_(0.02))₉₆Zr₄ wasfound to be a metallic glassy alloy having a ΔTx value as large as thatof Fe₅₅Pt₂₅(Si_(x)B_(y)P_(z))₂₀ (wherein, 11≦x<19 at %, 0≦y<8 at %, and0<z<8 at %). It was also found that the L1₀-FePt phase is generated byannealing at 800 K for 900 seconds, and that hard magnetic property wasobtained.

Comparative Examples are explained below.

Comparative Example 1

The alloy in Comparative Example 1 was manufactured by the same methodas Example 1, except that the chemical composition was changed toFe₅₅Pt₂₅Si₈B₈P₄. The DSC trace revealed that this alloy was not ametallic glass.

Comparative Example 2

The alloy in Comparative Example 2 was manufactured by the same methodas Example 1, except that the chemical composition was changed toFe₅₅Pt₂₅Si₁₀B₈P₂. The DSC trace revealed that this alloy was not ametallic glass.

According to Examples and Comparative Examples described above, it isidentified to be able to manufacture metallic glasses having a large ΔTxin Fe₅₅Pt₂₅(Si_(x)B_(y)P_(z))₂₀ (wherein, 11≦x<19 at %, 0≦y<8 at %, and0<z<8 at %) and (Fe_(0.55)Pt_(0.25)Si_(0.16)B_(0.02)P_(0.02))₉₆Zr₄. Itis obvious that the crystalline phase of L1₀-FePt can be generated bythe heat treatment and that the hard magnetic property can be obtained.

The embodiments of the present invention are not limited to thosedescribed above. Various modifications are possible without departingfrom the scope of claims of the present invention. It is needless to saythat those modifications are also included in the scope of the presentinvention.

1. A metallic glass comprising a chemical composition of said metallicglass is represented by the formula (1):Fe_(m)Pt_(n)Si_(x)B_(y)P_(z) (wherein, 20<m≦60 at %, 20<n≦55 at %,11≦x<19 at %, 0≦y<8 at %, and 0<z<8 at %)  (1).
 2. The metallic glass asset forth in claim 1, wherein the chemical composition is represented bythe formula (2):Fe₅₅Pt₂₅(Si_(x)B_(y)P_(z))₂₀ (wherein, 11≦x<19 at %, 0≦y<8 at %, and0<z<8 at %)  (2).
 3. A metallic glass comprising a chemical compositionis represented by the formula (3):(Fe_(0.55)Pt_(0.25)Si_(0.16)B_(0.02)P_(0.02))_(100-x)M_(x) (wherein,0<X≦6 at %; and M represents an element or a combination of any two ofmore of the elements selected from Zr, Nb, Ta, Hf, Ti, Mo, W, V, Cr, Mn,Al, Y, Ag, and rare earth elements.)  (3).
 4. The metallic glass as setforth in claim 3, wherein the M represents Zr.
 5. The metallic glass asset forth in any one of claims 1 to 3, wherein a part of Fe issubstituted by Co or Ni.
 6. The metallic glass as set forth in claims 1to 3, wherein a part of Pt is substituted by Pd. 7-20. (canceled) 21.The metallic glass as set forth in any one of claims 1 to 3, wherein aribbon of said metallic glass has a thickness of several μm to severaldozen μm.
 22. The metallic glass as set forth in any one of claims 1 to3, wherein said metallic glass is a form of powder.
 23. The metallicglass as set forth any one of claims 1 to 3, wherein said metallic glasshas the hard magnetic property.
 24. The metallic glass as set forth inclaim 1 or 2, wherein said metallic glass has the composition selectedfrom any one of Fe₅₅Pt₂₅Si₁₃B₅P₂, Fe₅₅Pt₂₅Si₁₆B₂P₂, Fe₅₅Pt₂₅Si₁₈P₂,Fe₅₅Pt₂₅Si₁₅B₃P₂, Fe₅₅Pt₂₅Si₁₁B₁P₈, Fe₅₅Pt₂₅Si₁₃B₁P₆, Fe₅₅Pt₂₅Si₁₃B₃P₄,Fe₅₅Pt₂₅Si₁₄B₄P₂, Fe₅₅Pt₂₅Si₁₅B₁P₄, Fe₅₅Pt₂₅Si₁₅B₂P₃, Fe₅₅Pt₂₅Si₁₅P₅,Fe₅₅Pt₂₅Si₁₆B₃P₁, and Fe₅₅Pt₂₅Si₁₇B₃.
 25. The metallic glass as setforth in claim 24, wherein a supercooled liquid temperature region ΔTx(=Tx−Tg) is ranged from 17K, 23K, 25K, 31K, 32K, and 37K.
 26. Themetallic glass as set forth in claim 24, wherein said metallic glass hasa composite structure consisting of L1₀-FePt phase, Fe₂B phase, PtSiphase, and FeSi phase.
 27. The metallic glass as set forth in claim 24,wherein said metallic glass has a composite structure consisting ofL1₀-FePt phase, fcc-FePt phase, FeSi phase, and Pt₂Si₃ phase.
 28. Themetallic glass as set forth in claim 24, wherein said metallic glass hasthe hard magnetic property.
 29. The metallic glass as set forth in claim3, wherein said metallic glass has the composition of(Fe_(0.55)Pt_(0.25)Si_(0.16)B_(0.02)P_(0.02))₉₆Zr₄.
 30. The metallicglass as set forth in claim 29, wherein a supercooled liquid temperatureregion ΔTx (=Tx−Tg) is 48K.
 31. The metallic glass as set forth in claim29, wherein said metallic glass has a composite structure consisting ofL1₀-FePt phase.
 32. The metallic glass as set forth in claim 29, whereinsaid metallic glass has the hard magnetic property.